1. Field of the Invention
The present invention relates to a stereoscopic image display device. More specifically, the present invention relates to a stereoscopic image display device which displays images that correspond to each of a plurality of viewpoints, a terminal device that is provided with the stereoscopic image display device, a stereoscopic image display method, and a program thereof.
2. Description of the Related Art
Conventionally, there is a stereoscopic image display devices capable of achieving stereopsis without using eyeglasses through providing images different from each other towards a plurality of viewpoints and projecting images of different parallax to the left and right eyes of the observer.
As a stereoscopic image display method employed with such device, known is a method which: synthesizes image data for each of the viewpoints and displays it on a display unit; separates the displayed synthesized image by an optical separating module constituted with a lens or a barrier (a light-shielding plate) having a slit; and provides those to each of the viewpoints of the observer.
As the optical separating device, generally employed are a parallax barrier having a great number of striped slits and a lenticular lens in which cylindrical lenses having the lens effect in one direction are arranged.
With the stereoscopic image display device employing such display method, it is necessary to project appropriate parallax images to each of the left and right eyes of the observer. Thus, the space region (stereopsis region) where the observer can properly observe the stereoscopic image is limited. Therefore, when the positions of the left and right eyes of the observer are shifted out of the stereopsis region, the appropriate stereoscopic image cannot be visually recognized due to the existence of a crosstalk region where the parallax images overlap with each other so that a double image is visually recognized and a reverse view region where each of the parallax images is projected inversely.
As a method for improving such issue, there is a method which detects positions of the eyes of the observer and executes switching control of parallax images by using the detection result, and known is a display device in which the visibility of the stereoscopic images is improved in the crosstalk region and the reverse view region by employing that method (e.g., Japanese Patent Publication H 10-333091 (Patent Document 1), Japanese Unexamined Patent Publication 2011-215499 (Patent Document 2), Japanese Unexamined Patent Publication 2012-120194 (Patent Document 3), Japanese Unexamined Patent Publication 2012-60607 (Patent Document 4), and Japanese Unexamined Patent Publication 2005-91447 (Patent Document 5)).
Patent Document 1 discloses a technical content which executes parallax barrier control and image switching control in a stereoscopic image display device in which the resolution of the parallax barrier is doubled, when the observer is in a crosstalk region or a reverse view region. Further, the display device disclosed in Patent Document 2 includes: a light source unit having definition of four times of 3D resolution on the backlight side; and a light source control unit for controlling the light source unit. Disclosed therein is a technical content with which the light source control unit executes switching control of the functions of the light source that constitutes the light source unit according to the position of the observer.
That is, disclosed in Patent Documents 1 and 2 are the display devices which present images of less sense of uncomfortable feeling according to the detected position of the observer through having a light-ray distribution module exceeding the resolution of the display panel. In those display devices, the number of device viewpoints (the number of regions where the so-called parallax images are to be projected) determined according to the relation between the display panel and the light-ray distribution module is increased to take a countermeasure for reverse view.
In the image display device disclosed in Patent Document 3, a sense of uncomfortableness felt at the time of viewing is suppressed with a technique which sets off the parallax barrier function and outputs 2D images when it is detected that there are a plurality of observers. Further, in the stereoscopic image display device disclosed in Patent Document 4, a sense of uncomfortableness is lightened with a technique which controls the parallax amount according to the position of the observer.
Patent Document 5 discloses a technical content with which a lobe control module constituted by including a parallax barrier executes switching control of the stereopsis region to achieve multi-viewpoints by using side lobes even in a case where tracking is not used. Further, in the stereoscopic display device, a sense of uncomfortableness felt when one of the eyes of the observer is located in the main lobe and the other eye is located in the side lobe through a technique that is a combination of tracking and the processing by the lobe control module.
However, there are following issues with the display devices according to each of Patent Documents described above which employ the switching control of the parallax images based on the detected result regarding the positions of both eyes of the observer.
With the display device disclosed in Patent Document 1 or 2, a high-definition light-ray separating module having the resolution of twice or more of the display panel is required. This causes increase in the cost for the structure or manufacture. Further, while prescribed image processing can be performed within the range of the number of the viewpoints of the device, it is only possible to present repeated videos to be visually recognized for the viewing angles over the number of viewpoints of the device.
Further, Patent Documents 3 and 4 disclose the image display device employing the structure that makes it possible to effectively work within the number of viewpoints of the device. That is, no technical measure for suppressing the deterioration of the image quality in the reverse view region is employed, so that a sense of uncomfortableness is to be felt when visually recognizing the images in the reverse view region. Furthermore, a parallax barrier is provided as a lobe control module in Patent Document 5, so that the transmittance is low.
It is an exemplary object of the present invention to improve the shortcomings of the related techniques and, more specifically, to provide a stereoscopic image display device and a terminal device, which generate and display significant parallax images corresponding to the position of the observer.